nbsUserSessionVia indicates the type of session, such as console, ssh, telnet, api, snmp, or gui, per its description, noting that this field is decided by the system rather than stored in the utmp file. An admin uses this to see how a user reached the device, which matters for security review, since an unexpected access method (like telnet on a device that should only allow ssh) is itself worth flagging. For example, an admin might audit nbsUserSessionTable specifically for rows where nbsUserSessionVia is telnet(3) if telnet access is supposed to be disabled.